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Effect of Surface Texturing on Friction and Film Thickness under Starved Lubrication Conditions
Ali, Fadi ; Kaneta, Motohiro (oponent) ; Glovnea, Romeo (oponent) ; Hartl, Martin (vedoucí práce)
This PhD thesis focuses on studying the effects of shallow micro-textures on friction and film thickness of lubricated non-conformal contacts under extreme and starved conditions. Measurements were carried out using a ball-on-disc tribometer equipped with high speed camera and torque sensor. Two types of micro-textures have been assessed in this study, micro-dents and transverse micro-grooves. The results reveal that micro-dents are helpful in reducing friction under starved conditions due to the film thickness enhancement. The mechanism of filling the depleted micro-dents with fresh lubricant is probably attributed to the capillary effect in the inlet zone under starvation. On the other hand, the rubbing surfaces with transverse shallow micro-grooves with a length less than the diameter of the Hertzian contact have an improved tribological performance in comparison with smooth surfaces. Indeed, transverse shallow micro-grooves showed a significant enhancement of film thickness under starvation and under extreme operating condition (reverse motion). The numerical simulation of the transient behavior of transverse limited micro-grooves showed accepted agreement with experimental results.
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Effects of Non-Newtonian Lubricants on Surface Roughness in Point Contacts
Ficza, Ildikó ; Kaneta, Motohiro (oponent) ; Poll, Gerhard (oponent) ; Hartl, Martin (vedoucí práce)
This PhD thesis focuses on the study of roughness deformation inside an elastohydrodynamically lubricated point contact. The passage of the roughness feature through the contact zone is modeled using numerical techniques. A single transverse ridge is assumed in the transient EHL model which presents a complex problem with a second order partial differential equation an integro-differential equation. Non-Newtonian fluid behavior is assumed in the model which further increases its complexity. In order to solve the system of equations the multigrid techniques are applied. The thesis contains the mathematical model describing the problem and a detailed description of the multigrid method. The results obtained by the simulations are compared to experimentally evaluated film thickness values. The roughness deformation is observed for a wide range of operating conditions as well as for different lubricant parameters. The effect of these lubricant parameters on the deformation is studied as well.
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Effect of Surface Texturing on Friction and Film Thickness under Starved Lubrication Conditions
Ali, Fadi ; Kaneta, Motohiro (oponent) ; Glovnea, Romeo (oponent) ; Hartl, Martin (vedoucí práce)
This PhD thesis focuses on studying the effects of shallow micro-textures on friction and film thickness of lubricated non-conformal contacts under extreme and starved conditions. Measurements were carried out using a ball-on-disc tribometer equipped with high speed camera and torque sensor. Two types of micro-textures have been assessed in this study, micro-dents and transverse micro-grooves. The results reveal that micro-dents are helpful in reducing friction under starved conditions due to the film thickness enhancement. The mechanism of filling the depleted micro-dents with fresh lubricant is probably attributed to the capillary effect in the inlet zone under starvation. On the other hand, the rubbing surfaces with transverse shallow micro-grooves with a length less than the diameter of the Hertzian contact have an improved tribological performance in comparison with smooth surfaces. Indeed, transverse shallow micro-grooves showed a significant enhancement of film thickness under starvation and under extreme operating condition (reverse motion). The numerical simulation of the transient behavior of transverse limited micro-grooves showed accepted agreement with experimental results.
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Effects of Non-Newtonian Lubricants on Surface Roughness in Point Contacts
Ficza, Ildikó ; Kaneta, Motohiro (oponent) ; Poll, Gerhard (oponent) ; Hartl, Martin (vedoucí práce)
This PhD thesis focuses on the study of roughness deformation inside an elastohydrodynamically lubricated point contact. The passage of the roughness feature through the contact zone is modeled using numerical techniques. A single transverse ridge is assumed in the transient EHL model which presents a complex problem with a second order partial differential equation an integro-differential equation. Non-Newtonian fluid behavior is assumed in the model which further increases its complexity. In order to solve the system of equations the multigrid techniques are applied. The thesis contains the mathematical model describing the problem and a detailed description of the multigrid method. The results obtained by the simulations are compared to experimentally evaluated film thickness values. The roughness deformation is observed for a wide range of operating conditions as well as for different lubricant parameters. The effect of these lubricant parameters on the deformation is studied as well.
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